Sulfur-hydrocarbon slurry pipeline transportation

ABSTRACT

AN IMPROVED METHOD OF TRANSPORTING SULFUR-LIQUID HYDROCARBON SLURRIES THROUGH PIPELINES WITHOUT CAUSING PLUGGING OR CORROSION OF THE PIPELINES. THE INVENTION RELATES TO AN IMPROVED AND NOVEL PROCESS OF PREVENTING CORROSION OF PIPELINES TRANSPORTING SULFUR IN THE FORM OF A SULFUR-LIQUID HYDROCARBON SLURRY.

United States Patent Inventor Mary Frances Vondrak Houston, Tex.

Appl. No. 772,011

Filed Oct. 30, 1968 Patented June 28, 1971 Assignee Shell Oil Company New York, N.Y.

SULFUR-HYDROCARBON SLURRY PIPELINE TRANSPORTATION 8 Claims, No Drawings US. Cl 302/66, 302/ 1 4 Int. Cl 865g 53/04 Field 01 Search 302/14, 15,

16,66, (lnquired) [56] References Cited UNITED STATES PATENTS 2,711,391 6/1955 Kahlerm. 302/66 2,798,772 7/1957 Redcay 302/14 Primary Examiner-Andres H. Nielsen AtrorneysGeorge G. Pritzker and J. H. McCarthy SULFUR-HYDROCARBON SLURRY PIPELINE TRANSPORTATION BACKGROUND OF THE INVENTION The transportationof sulfur neat or as a water or oil slurry in pipelines is well known in the art as noted by reference to U.S. Pat. Nos. 2,798,772; 2,917,345 or 2,947,578 or as described in Pipeline Industry, June, 1967, pages 58-60. In making the sulfur into a sulfur-hydrocarbon slurry, the sulfur is generally sprayed in molten form into either water or a hydrocarbon to form a slurry suitable for transportation through a pipeline. Formation of a stable slurry wherein the sulfur does not undergo any undesirable change or the slurry does not exhibit a tendency to .wide variation in viscosity is essential to the process in addition to other problems which may be encountered during and after transportation of the slurry through a pipeline. Thus, separation of the sulfur from the carrier fluid, plating or coating of the sulfur on pipeline walls causing plugging of the pipeline, corrosion, viscosity changes due to pressure and temperature variations encountered requiring increases in pumping power which increases operation costs, etc., are only a few of the problems normally encountered in transporting sulfur-liquid hydrocarbon slurries through pipelines.

Although the above are serious problems for consideration in transporting sulfur through pipelines, nevertheless the transportation of sulfur in slurry form through pipelines can be made to be an effective, attractive and economic means of transportation, particularly since sulfur is recovered or obtained from isolated, remote and inaccessible'areas, and must be transported to desired accessible areas. As noted above, a number of methods have been proposed for pipeline transportation of sulfur slurries such as injecting molten sulfur into water or a liquid hydrocarbon thereby forming a sulfur slurry for pipeline transportation. Such means for transporting sulfur generally do not overcome the corrosion, coating and/or plugging problems described above.

An object of the present invention is to transport sulfur as a sulfur-liquid hydrocarbon slurry through pipelines which is stable and flowable.

Still another object of the present invention is to transport through a pipeline sulfur-liquid hydrocarbon slurries without causing sulfur coating, deposition or plugging or corrosion of the pipeline.

Still another object of this invention is to form a slurry of sulfur in a liquid hydrocarbon medium, which when formed is stable, noncorrosive, does not tend to cause pipeline plugging when said slurry is transported through a pipeline and from which the sulfur can be readily recovered as essentially pure sulfur.

Another object is to transfer sulfur as a liquid hydrocarbon slurry by pipeline over great distances under conditions of reduced pumping and handling costs.

Other objects will be apparent from the following descript1on.

SUMMARY OF THE INVENTION The present invention is directed to an improved, novel and new technique for transporting a sulfur-liquid hydrocarbon slurry through pipelines over great distances without causing corrosion, or sulfur deposition on the walls of the pipeline due to the tendency of sulfur under such conditions to adhere to the pipeline walls because of temperature, pressure and other variable conditions to corrode and plug said lines; by admixing or adding or injecting prior to or after injection of a sulfurliquid hydrocarbon slurry into the pipeline, a small amount of from 0.1 percent by weight to 10 percent by weight, preferably between about 0.5 percent by weight to about 5 percent by weight of an aqueous solution basis total slurry containing therein from about 0.1 percent byweight to about 5 percent by weight of sodium chromate basis aqueous solution. The aqueous solution containing sodium chromate in an amount preferably not exceeding 5 percent by weight basis aqueous solution and having a pH greater than 7 can be injected when necessary in various places along the pipeline where indications are that corrosion or plugging of the line might take place. Any corrosion and plugging detection means known in the art can be used for this purpose. It has been noted that by injection of 1-5 percent by weight of an aqueous solution basis total slurry containing a small amount l 2 percent by weight) of sodium chromate basis aqueous solution into a pipeline transporting a sulfur-liquid hydrocarbon slurry in which the sulfur content of the slurry can vary from about 10 percent by weight to about 75 percent by weight or higher, preferably between 30 and 70 percent sulfur not only inhibits corrosion but prevents plugging of the line due to sulfur deposition on the walls of the pipeline resulting in improved flow of the slurry at reduced pumping cost. A preferred plugging and corrosion preventing composition for sulfurliquid hydrocarbon slurries being pipeline transported is the addition to such slurries of from l-5 percent by weight water basis total slurry containing 1-2 percent by weight Na CrO, basis aqueous solution having a pH of above 7 (7.5-9.5).

The sulfur-liquid hydrocarbon slurry can be made by any suitable means such as described in U. S. Pat. 2,798,772 or by the method described in copending patent application Ser. No. 663,755 filed Aug. 28, 1967 which issued as U.S. Pat. 3,443,827. It is preferred that methods for making the sulfurliquid hydrocarbon slurry be used in which the sulfur is produced in spherical form since this facilitates the stable dispersion and suspension of the sulfur in the liquid hydrocarbon carrier and inhibits attrition and reduces friction. The phase transfer method for making the sulfur slurry as described in the above copending application comprises first forming a sulfur-aqueous liquid (water) slurry and thereafter phase transferring the sulfur particles from the aqueous liquid into a liquid hydrocarbon. In this process the phase transformation to form the sulfur-hydrocarbon slurry can be so controlled that a small amount (1-5 percent by weight) water basis total slurry is transferred with the sulfur-water phase into the hydrocarbon phase and thereafter sodium chromate can be added to accomplish the desired ends of the present invention.

The hydrocarbon carrier for the sulfur can be any liquid hydrocarbon carbon ranging from a light petroleum fraction such as liquefied petroleum gas (LPG), fuel oil, gasoline, kerosene, petroleum distillates, condensates, crude oil and mixtures thereof. Preferred are liquid hydrocarbons containing at least 10 percent by weight or higher of aromatics, preferably about 15-30 percent by weight aromatic enriched kerosene or crude oil condensate fractions containing 15-20 percent by weight aromatics which include monoand polyaromatic hydrocarbons.

At the terminal end of the line the aqueous solution can be readily separated from the sulfur-hydrocarbon system by suitable phase separation, distillation or the like.

PREFERRED EMBODlMENT OF THE INVENTION A 40-60 percent by weight sulfur-aromatic (17 percent) enriched kerosene slurry was prepared by phase transfer by first injecting molten sulfur into an aqueous liquid such as water and thereafter contacting the slurry thus formed with the aromatic enriched kerosene to effect phase transfer of the sulfur particles into the aromatic enriched kerosene, and injecting this slurry into a pipeline followed by injection of 1-5 percent by weight water solution basis total slurry containing about l-2 percent by weight Na CrO basis aqueous phase. Sulfur-hydrocarbon slurries thus formed in the presence of the sodium chromate solution do not corrode or plug the pipeline. instead of using the phase transfer technique for making the slurry, the molten sulfur can be injected in the kerosene directly and thereafter admixed with the sodium chromate solution.

An advantage of the present process for transporting through pipelines sulfur-liquid hydrocarbon slurries is that the slurry can be also prepared by directed in ection of molten sulfur into a suitable liquid hydrocarbon as described in U.S. Pat. 2,798,772 and injecting therein a small amount of sodium chromate water solution so as to prevent corrosion and plugging of the line. Either process as well as other processes can be used to make the sulfur-liquid hydrocarbon slurry depending on the availability of the liquid carriers Thus, where water is available the first process can be used and if not the second one can be used.

The corrosive effect of added or adventitious water on sulfur-liquid hydrocarbon slurries is evident from the data presented in Table l and the selectiveness and unexpected effect of Na CrQ, as a corrosion preventive agent is shown in Table 2 where the effectiveness of Na CrO and the ineffectiveness of well-known inhibitors is compared.

The slurry tested comprised 40 percent by weight sulfur and 60 percent by weight aromatic enriched kerosene. The conditions for the corrosion test were as follows:

Corrosion by Sulfur Slurries Conditions: 150 ml magnesia bottles rotated at 10 rpm. in EPR bottle rotator, Mark ll; 48 hours.

l20 grams of slurry added to each bottle. Slurry concentration 40 percent by weight Watenon sulfur.

Sulfur particle size 82 percent greater than 45'microns.

Oil phase: Kerosene with 17 percent by weight aromatics.

Water and solution additions are percent by weight of oil fraction.

6'wia-inch specimens of 20 gauge mild steel sheet with sandblasted surface. Specimens wedged into bottles to reduce mechanical damage.

Room temperature (70), atmospheric pressure.

sulfur Slurry Corrosion as a Function of Water Concentration Corrosion rate,

Water concentration, percent w. mils/yr. 1

B Concentration of added water, basis oil. b From weight loss and exposure time.

TABLE 2 Sulfur Slurry Corrosion Corrosion Additive a pH b rate (m.p.y.) c

1.0% Na CrOi l l. 9.? 2 2.0% NazCroi 9. 2 3 1% ZnS O 6.0 0.6% NaOH plus 0.6% ZnSO 12.2 25 1.3% Na acetate T. 9 105 1.0% acetic acid 2. 7 140 0.6% Na acetate plus 0 ad 0 aci 4. 5 190 1.0% Na benzoate 7.0 40

a All aqueous solution additions were made at 2% n. basis oil. The salt and acid concentrations are percent by weight basis aqueous solution.

' The pH is that of the solution before addition to the slurry.

@ From weight loss and exposure time.

At the terminal end of the line the water phase can be readily removed by phase separation and the sulfur can be removed from the liquid hydr carbon by suitable means such as described in US. Pat 2. 98.772 and the sulfur purified by methods as described in US. Pat. 2,809,885 or as described in the copending Pat. application Ser. No. 684,507, filed Nov.

receiving terminal the sulfur slurry can be filtered and washed. The recovered sulfur is then melted and purified by liquidliquid extraction with an aromatic hydrocarbon such as oumene. Also if desired, the filtered sulfur can be steam stripped to recover bright yellow sulfur.

The foregoing description of the invention is merely intended to be explanatory thereof. Various changes in the details of the described method may be made within the scope of the appended claims without departing from the spirit of the invention.

I claim:

1. A method of transporting sulfur through a pipeline to a terminal preventing corrosion and without plugging the line comprising:

a. injecting molten sulfur into a liquid hydrocarbon to form a sulfur-liquid hydrocarbon slurry;

b. mixing with the slurry (a) from about 0.1 percent to about 10 percent of an aqueous solution containing from about 0.01 percent to about 5 percent of sodium chromate;

c. injecting the mixture of (a) and (b) into a pipeline; and,

d. transporting the slurry containing the sodium chromate solution through a pipeline to a terminal station.

2. The method of claim 1 wherein the liquid hydrocarbon of (a) contains at least 10 percent aromatic components.

3. The method of claim 1 wherein solution (b) is injected into the slurry (a) after the slurry (a) has been injected into a pipeline.

4. The method of claim 1 wherein the slurry (a) contains 10-75 percent by weight sulfur and the balance being a liquid hydrocarbon containing aromatic components and the amount of solution (b) added to slurry (a) is from 0.1 to 10 percent by weight basis total slurry and said solution (b) contains from 0.01 to 5 percent by weight Na CrO basis aqueous phase.

5. The method of claim 4 wherein solution (b) is water containing l-2 percent by weight Na CrO basis aqueous solution admixed with slurry (a) in amounts of from 1 to 5 percent by weight basis total slurry.

6. The method of claim 1 wherein at the terminal end, the slurry is separated into its separate components of sulfur and liquid hydrocarbon.

7. The method of claim 5 wherein the separation of the slurry into its sulfur and liquid hydrocarbon components is effected by treatment of the slurry with an aqueous solution containing a mixture of alkali hydrosulfide and corresponding hydroxide.

8. The method of claim 6 wherein the aqueous solution contains a mixture of ammonium hydrosulfide and ammonium hydroxide. 

